Most of the moisturizing lotions and ointments commonly used to treat and protect mammalian skin consist of oil-in-water emulsions and creams, water-in-oil emulsions and, to a lesser degree, simply oil-based formulations. The oils used are selected from a large group of cosmetically accepted oils, which are generally recognized by the cosmetic industry for use on skin. Preferred oils have emollient properties. As a whole, these products either do not allow or do not enhance the ability of adhesive products, such as medical tapes, to adhere to skin to which they have been applied.
It is known that certain oil-soluble acrylate polymers, alone or in combination with conventional moisturizing oils, in oil-in-water or water-in-oil emulsions, provide skin treatments. For example, oil-soluble acrylate polymers have been used in sunscreening compositions of the water-in-oil type to reduce removal of the sunscreening agent from the skin by swimming or perspiration; in skin moisturizing compositions; with medicaments for topical application to the skin; in mosquito repellent compositions; and in cosmetic compositions such as lip rouges, mascaras, and eyeliners. Such skin treatments that are substantive (i.e., they are not readily removed by simple abrasion or water assault) are particularly desirable.
Water-in-oil emulsion compositions for skin treatment containing low molecular weight oil-soluble acrylate copolymers as emulsifying agents are disclosed in U.S. Pat. No. 4,552,755 (Randen et al.) and U.S. Pat. No. 6,200,596 (Swartzmiller). When these oil-soluble acrylate polymers are used with emollient oils in oil-in-water or water-in-oil emulsions, the result is a skin treatment that provides long lasting skin moisturizing effects. Also, unexpectedly, these compositions enhance (or do not significantly inhibit) the ability of pressure sensitive adhesives to adhere to treated skin. These polymers are prepared from carboxylic acid functional monomers such as acrylic acid, which until the present invention were believed to be important for adhesion of pressure sensitive adhesives. Such products are considered to have high substantivity on tissue.
U.S. Pat. No. 4,172,122 (Kubik et al.) teaches that carboxylic acid functional monomers such as acrylic acid are important in preparing acrylate polymers that can be used in products such as sunscreening products to reduce removal of the sunscreening agent from the skin by swimming or perspiration. Such products are considered to have high substantivity on tissue.
It has also been the conventional belief that carboxylic acid functional monomers, such as acrylic acid, were important for preparing stable water-in-oil emulsions. There is a desire, however, to eliminate such acidic components in products used on skin, particularly because they can deactivate antimicrobial agents, for example. Furthermore, it has been found that the carboxylic acid functional polymers are typically not capable of stabilizing water-in-oil emulsions at low pH, e.g., pH of less than about 5 and especially less than about 4.5. Thus, there is a need for water-in-oil emulsions that are preferably stable over a broad range of pH (e.g., about 3 to about 12) and that preferably do not include acidic components.